As a prior art, Japanese Patent Application Publication No. 2006-511078 (JP2006-511078A) discloses a power supply assembly for an LED illumination module that performs dimming control on an LED by combining low-frequency PWM (Pulse Width Modulation) control with a high-frequency PWM control. This device includes a switch mode converter for supplying a constant current to the LED illumination module, and a dual PWM signal composed of low frequency bursts of high frequency pulses is provided to the control switch of the switch mode converter. By varying the average current flowing through the LED illumination module as the low-frequency component of the dual PWM signal is varied, the intensity of a light outputted from the LED illumination module is changed.